This invention relates to hydraulic system, and particularly to a hydraulic system wherein a hydraulic function without load pressure sensing capability is supplied with fluid from the pump of a closed center hydraulic system with load pressure sensing.
Some agricultural tractors have closed centered pressure and flow compensated (POD) hydraulic systems. In contrast, some implements to be connected to agricultural tractors have hydraulic systems or components which are designed for constant pressure hydraulic systems. Thus, when a tractor control valve of such a tractor hydraulic system is used as the source of hydraulic fluid for one or more controlled hydraulic functions on an implement with such an implement hydraulic system, this results in the tractor running at maximum system operating pressure which generates higher power consumption resulting in increased fuel consumption and additional heat generation.
One solution to this problem is to equip the tractor with a non-controlled pressure source and a return source and to install a hydraulic load sense line on the implement which senses the hydraulic pressure of the implement function. This approach requires modification of the implement hydraulics (circuitry or valving) and can become very complicated and expensive when multiple functions are involved.
A second solution involves using valve packages typically supplied for implements with closed centered hydraulic systems when they are connected to tractors with open centered hydraulic systems. This valve package uses an implement electrical control signal to operate an unloading valve in the valve package. In this mode of operation, the operator must carefully adjust the tractor valve, which supplies the flow, to minimize power loss. Even with this adjustment, flow is continuous even when the implement functions are not operating and thus wasting power. It would be desirable to provide a solution which avoids the above described problems.